The present invention pertains to a reflective display for use in a vehicle for preventing polarization of the reflected image of the displayed information such that a viewer wearing polarized sunglasses can see the information being displayed.
There exists a variety of modern display systems for displaying to a vehicle operator or occupants of a vehicle such as an automobile, information as to the vehicle operating status. Such displays include, for example, heads-up displays which are projected on the windshield, vacuum-fluorescent displays included directly in the instrument panel, liquid crystal displays, and reflective displays used in connection with vehicle accessories such as overhead consoles or rearview mirrors. U.S. Pat. application Ser. No. 07/567,390, filed Aug. 14, 1990, entitled ELECTRICAL CONTROL SYSTEM FOR VEHICLE OPTIONS, discloses the latter type of reflective display for use in a rearview mirror assembly. U.S. patent application Ser. No. 07/745,454, filed Aug. 14, 1991, entitled REFLECTIVE DISPLAY AT INFINITY, discloses a display which can be incorporated into a vehicle overhead console.
In displays employed in high ambient light conditions, such as encountered in vehicles such as automobiles during daylight use and particularly displays located in the upper windshield area where incoming sunlight tends to interfere with a display presentation, it is necessary to provide a relatively high-contrast display so that a vehicle operator can clearly see a display even under such interfering high ambient light. This has been achieved by employing a reflective shiny surfaced, black polycarbonate or acrylic material which receives the reversed image source information from a vacuum-fluorescent display and reflects such information to provide the vehicle operator with a relatively bright and contrast display.
In relatively small vehicle accessories, such as a rearview mirror housing and compact overhead consoles, it is desirable to provide a reflective display which allows the display of information from, for example, a vacuum-fluorescent source, to be positioned within a housing and a reflective target positioned on the outer edge of the housing for compact packaging of such accessories including displays. In rearview mirrors, this compact packaging structure does not detract from the available surface area of the rearview mirror itself. In providing a reflective display with a light source located, for example, below the target, it is necessary to align the target at an angle of approximately 45.degree. to project the image to the viewer's eyes. This angle is relatively close to Brewster's Angle for polymeric material used as a target in which the parallel (sometimes referred to as vertical) component of the light is almost totally absorbed reflecting only the perpendicular (sometimes referred to as horizontal) component of reflected light. As a result, in such display systems the light reflected from the target to the viewer's eyes is polarized and comprises substantially only the perpendicular component. The serendipitous discovery of this problem became apparent only when one wearing sunglasses which were polarized could not see the display.
Thus, it was discovered that the utilization of an angled reflective black acrylic or other polymeric material as a target, although providing a high-contrast display usable under most light conditions, also polarizes the light received and reflects primarily only the perpendicular component of incident light. As a result, if an individual is wearing polarized sunglasses, as frequently occurs in high ambient sunlight conditions, the display information is blocked out by the interfering polarization patterns of the polarized sunglasses and the polarizing effect of the reflective material. The unfortunate result is that the display is not visible to an individual wearing polarized sunglasses.